JP4337581B2 - Semiconductor wafer double-side polishing apparatus and crack inspection method - Google Patents

Description

  The present invention relates to a double-side polishing apparatus for a semiconductor wafer such as a silicon wafer, and a method for inspecting whether or not a wafer has been cracked after double-side polishing of a semiconductor wafer.

Conventionally, a single-side polishing apparatus and a double-side polishing apparatus have been used as apparatuses for polishing a semiconductor wafer such as a silicon wafer.
As a general double-side polishing apparatus, a so-called four-way type apparatus 50 using a planetary gear mechanism as shown in FIGS. 6 and 7 is known.

  When the silicon wafer W is polished by such a double-side polishing apparatus 50, the wafer W is inserted and held in a plurality of wafer holding holes 58 formed in the carrier 51. Then, the wafer W in the holding hole is sandwiched between the upper surface plate 56a and the lower surface plate 56b to which the polishing cloths 57a and 57b are respectively attached, the polishing slurry is supplied through the slurry supply hole 53, and the carrier 51 is connected to the sun gear 54 and the internal gear. Rotate and revolve with the gear 55. Thereby, both surfaces of the wafer W in each holding hole can be polished simultaneously.

  As another type of double-side polishing apparatus, for example, as shown in FIGS. 8 and 9, the carrier 31 sandwiched between upper and lower surface plates 36a and 36b (polishing cloths 37a and 37b) is not rotated. There is known a device 30 that swings so as to draw a small circle (see Patent Document 1). A carrier 31 having a holding hole 34 is held by a carrier holder 38, and an eccentric arm 40 is rotatably attached to a bearing portion 39 of the holder 38.

  At the time of polishing, all the eccentric arms 40 are rotated in synchronization with the rotation shaft 41 via the timing chain 42, so that the carrier 31 held by the carrier holder 38 does not rotate and is a small circle in the horizontal plane. You can do a circular motion like drawing. Since the swing-type double-side polishing apparatus 30 can be downsized, the polishing operation can be performed in a relatively narrow space. With the recent increase in diameter of wafers, a oscillating double-side polishing apparatus 30 is often used.

  More specifically, the polishing procedure by the double-side polishing apparatus 30 will be described. For example, a box (generally called FOSB, FOUP, etc.) containing 25 wafers is an automatic transfer apparatus (AGV or the like). ) To a predetermined position and placed in a loading station (loader unit) of the double-side polishing apparatus 30.

  Next, after the wafer in the box is set in each holding hole 34 of the carrier 31, both surfaces of the wafer W are sandwiched between upper and lower surface plates 36a and 36b (polishing cloths 37a and 37b). The upper and lower surface plates 36 a and 36 b are rotated and the carrier 31 is swung to supply the polishing slurry from the slurry supply hole 33. The slurry reaches the lower polishing cloth 37b through the slurry passage hole 35 and the like of the carrier 31, and is simultaneously polished when both surfaces of the wafer W are in sliding contact with the polishing cloths 37a and 37b, respectively. After polishing for a predetermined time, the movement of the surface plates 36a and 36b and the carrier 31 is stopped. And the wafer W in the holding hole 34 is carried out to an unloading station (unloader part), maintaining a wet state, and is collect | recovered in the container (water tank) for collection | recovery.

  Conventionally, the operation of setting the wafer in the holding hole of the carrier and recovering the polished wafer from the carrier has been performed manually. However, in recent years, automation has progressed, and the loading of wafers in a box and unloading of wafers after polishing have been automatically performed by a transfer robot.

  For example, in a swing type double-side polishing apparatus, if the carrier holder has a mechanical positioning function (index function) and the carrier 31 has five holding holes 34 as shown in FIG. By positioning in such a manner, the wafers can be automatically set to the respective holding holes 34 one by one at a fixed position by the transport robot. In addition, after polishing, the carrier 31 can be similarly rotated to take out the wafers W one by one by the transfer robot.

As described above, the automation of the double-side polishing apparatus is progressing. However, for example, when a part of the wafer is polished in a state of protruding from the holding hole, the wafer may be broken during polishing. Such a cracked wafer can no longer be used as a product and must be removed.
Therefore, a process of inspecting the wafer for cracks before the polished wafer is taken out from the carrier by the transfer robot and recovered in the recovery container of the unloading station is required.

  Conventionally, in order to inspect for cracks in wafers, in addition to the method of visual confirmation by workers, a crack inspection station equipped with an optical sensor, etc. is installed, and the polished wafer is set in this inspection station. There is a method for inspecting cracks.

  For example, as a method of inspecting cracks and scratches on the outer periphery of the wafer, the wafer is placed horizontally on a rotary table and held by suction, and the intensity of diffracted light generated by irradiating the outer periphery of the wafer with light is increased. Based on this, a method for detecting defects such as scratches has been proposed (see Patent Document 2). According to this method, the entire circumference of the wafer can be continuously inspected by rotating the rotary table.

However, when such an inspection method is applied to a crack inspection of a polished wafer, it is necessary to temporarily set the polished wafer on a rotary table and to transport it to an unloading station after the inspection. For this reason, the number of times the wafer is transferred increases. Therefore, after polishing, the time until the wafer is transferred to the collection container of the unloading station becomes long, and there is a problem that productivity is lowered.
In addition, the wafer may be contaminated by an inspection rotary table or the like.

JP-A-10-202511 JP 2001-118894 A

  Therefore, the present invention automatically inspects the presence or absence of cracks in the polished wafer in a shorter time when polishing the semiconductor wafer automatically, has less influence on the unloading time, and makes double-side polishing of the wafer more efficient. It is an object of the present invention to provide a double-side polishing apparatus and a crack inspection method that can be carried out.

According to the present invention, there is provided a double-side polishing apparatus for a semiconductor wafer, wherein at least upper and lower surface plates, an abrasive cloth affixed to each surface plate, and the wafer are held between the upper and lower abrasive cloths during polishing. And a carrier robot for transporting the wafer before and after polishing, and means for inspecting whether or not the wafer is cracked in a state where the wafer after polishing is held by the transport robot. A double-side polishing apparatus is provided .

  In this way, in addition to a transfer robot that transfers wafers before and after polishing, a double-side polishing apparatus equipped with a means for inspecting the presence or absence of cracking of the wafer while holding the polished wafer by the transfer robot, During the transfer of the wafer to the unloading station, it is possible to inspect for cracks without placing the wafer on an inspection table or the like. Therefore, if this double-side polishing apparatus is used, the polished wafer can be inspected for cracks in a shorter time, and double-side polishing can be performed very efficiently without being contaminated by a table or the like. This also contributes to the automation of the entire polishing process.

The means for inspecting for cracks in the wafer includes an illuminating means for applying light to the surface of the polished wafer, an image detecting means for detecting an image of the wafer, and image data obtained by the image detecting means. Image processing means for performing image processing and determination means for determining the presence or absence of cracks in the wafer based on the brightness of the image processed image may be provided .
If the means for inspecting the crack has the illumination means, the image detection means, the image processing means, and the determination means as described above, even if the polished wafer is held by the transfer robot, Wafer cracks can be reliably detected by the brightness of the image.

In this case, the image detecting means is preferably a CCD camera or a vidicon camera .
For example, in the case of a CCD camera or a vidicon camera, the image on the wafer surface can be captured clearly and the presence or absence of cracks can be determined more reliably. In addition, since these cameras are small, the double-side polishing apparatus can be miniaturized.

Further, when the means for inspecting whether or not the wafer is cracked detects a crack, the operation of the broken wafer collecting means and / or the transfer robot for collecting the wafer separately from the wafer in which no crack is detected is stopped. Means are preferably provided .
Thus, if there is a means for collecting broken wafers and means for stopping the operation of the transfer robot, it is possible to distinguish and collect the wafers from which cracks are detected and normal wafers without cracks. The generated wafer can be surely removed.

Moreover, when the means for inspecting the presence / absence of cracks in the wafer detects a crack, alarm means for emitting an alarm sound may be provided .
If such an alarm means is provided, even if the worker is not constantly monitoring, the worker can be surely notified that the wafer has been cracked, and the operation of the apparatus is stopped afterwards. This measure can be taken appropriately.

Further, according to the present invention, after polishing a semiconductor wafer by a double-side polishing apparatus, the method for inspecting the presence or absence of cracking of the polished wafer, the semiconductor wafer is set on a carrier and affixed to upper and lower surface plates, respectively. Hold between the polishing cloths, supply the polishing agent and slide the upper and lower polishing cloths in contact with the polishing cloth, hold the polished wafer by the transfer robot, take it out from the carrier, and then put it on the unloading station A semiconductor wafer crack inspection method is provided, wherein the wafer is inspected for cracks in a state of being held by the transport robot before transport .

  Thus, after the polished wafer is held by the transfer robot and taken out of the carrier, before being transferred to the unloading station, the wafer is held by the transfer robot and inspected for cracks. For example, it is possible to inspect the presence of cracks in a short time without placing the wafer on the wafer, and the wafer is not contaminated. Therefore, it is possible to efficiently perform the polishing operation, greatly contribute to automation, and improve the wafer quality.

In this case, after polishing the semiconductor wafer and before removing from the carrier, the wafer is sprayed by at least one of the following methods: watering the wafer, rotating the lower surface plate, and rotating the carrier. It is preferable to remove the abrasive from the surface .
If abrasive bubbles are attached to the surface of the wafer after polishing, there is a risk of erroneous detection of cracks. However, if the abrasive is removed by applying water in advance, such erroneous detection is prevented. be able to.

It is preferable that the inspection of the semiconductor wafer for cracks is performed in a state where the wafer is held vertically or inclined .
If the wafer is held vertically or tilted in this way, the abrasive or water adhering to the surface will drip, and erroneous detection can be prevented more reliably.

It is preferable to inspect the presence or absence of cracks in the semiconductor wafer, apply light to the surface of the wafer, perform image processing on the image data obtained by the image detection means, and inspect the presence or absence of cracks in the wafer based on the brightness of the image. .
If light is applied to the surface of the wafer in this manner, the brightness of the cracked portion becomes clearer, so that the presence or absence of the crack can be more reliably determined.

When inspecting the presence or absence of cracks in the wafer based on the brightness of the image, it is possible to inspect the presence or absence of cracks in the area between the circular or elliptical double lines set inside the outer edge of the wafer. Is preferred .

  If cracks occur in the polished wafer, in most cases it is reflected in the area between the double lines set as described above, so it can be detected and the inspection area is narrow. The inspection can be performed in a shorter time.

  According to the present invention, the inspection of the semiconductor wafer after the polishing can be inspected for cracks before being transferred to the unloading station, with the wafer held by the transfer robot. Thus, the inspection can be performed efficiently in a short time. Therefore, it is possible to efficiently perform the polishing operation by quickly and reliably discriminating the wafer in which the crack is generated in the polishing process, greatly contributing to the automation of the double-side polishing process and improving the quality of the wafer. .

Hereinafter, as a preferred embodiment of the present invention, the case of double-side polishing a silicon wafer will be specifically described with reference to the accompanying drawings.
FIG. 1 shows an example of a double-side polishing apparatus according to the present invention. The double-side polishing apparatus 1 includes a polishing apparatus main body (polishing section) 2, a loading station (loader section) 10, an unloading station (unloader section) 16, a transport robot 13 that transports wafers before and after polishing. ing.

  The apparatus body 2 is a swinging type having an eccentric arm 7, a carrier holder 3, etc., and is attached to the upper and lower surface plates 8a and 8b and the surface plates 8a and 8b as shown in FIG. The polishing cloths 9a and 9b, the slurry supply means 33, the carrier 4 and the like are provided. In addition to the wafer holding hole 5, the carrier 4 is provided with a slurry passage hole 6. The apparatus main body 2 has an index function that can rotate (spin) the carrier 4 as well as swing.

Further, the apparatus 1 is provided with means (crack inspection means) 12 for inspecting whether or not the wafer is cracked in a state where the polished wafer is held by the transfer robot 13.
FIG. 3 shows an example of the configuration of the crack inspection means 12. The crack detection means 12 includes an illumination means (white fluorescent lamp) 22 that applies light to the surface of the wafer W held by the transfer robot 13 after polishing, and an image detection means (CCD camera) that detects an image of the wafer W. 21, image processing means (computer, monitor) 23 that performs image processing on the image data obtained by the image detection means 21, and determination means that determines the presence or absence of cracks in the wafer W based on the brightness of the image processed image ( Determination circuit) 24.
Note that each means is not limited to the above, and for example, a vidicon camera or the like can be used as the image detection means 21.

  Next, a procedure for polishing a silicon wafer and inspecting the wafer for cracks after polishing will be described with reference to an example of the polishing step shown in FIG.

  First, as shown in FIG. 1, the box 11 containing the wafer W to be polished is transported by the box automatic transport device 14 and placed on the loader unit 10. The method of transporting the box 11 to the loader unit 10 is not particularly limited. In addition to a method of transporting by a self-propelled transport vehicle (AGV) that travels on the floor surface, a rail is laid on the ceiling of the room. A method of transporting the box 11 along the rail (OHT) may be employed.

The box 11 arranged in the loader unit 10 is opened with a lid by an opener or the like. Then, the wafer W in the box 11 is set in the holding hole 5 of the carrier 4 by the transfer robot 13 (step (A) in FIG. 2).
If the transfer robot 13 has, for example, a holding means for scooping and holding the lower surface of the wafer W and a holding means for holding the upper surface by suction, the lower surface of the wafer W is removed from the box 11. After scooping up and taking out, and once placing on the centering stage 15, the upper surface can be sucked and held again. If the upper surface of the wafer W is sucked and held in this way, it can be reliably set in the holding hole of the carrier 4.

  Next, the upper surface plate 8a is lowered to hold the wafer W between the polishing cloths 9a and 9b attached to the upper and lower surface plates 8a and 8b, respectively. Then, the upper and lower surface plates are rotated in a predetermined direction, the abrasive is supplied from the slurry supply hole 33, and each wafer W in the holding hole is brought into sliding contact with the upper and lower polishing cloths 9a and 9b to perform double-side polishing ( Step (B) in FIG.

  After polishing for a predetermined time, the rotation of the surface plates 8a and 8b is stopped. After the stop, the upper surface plate 8a is moved upward, and the polished wafer is held by the transfer robot 13 and taken out from the carrier 4. The polishing agent is adhered to the surface of the polished wafer W, and the polishing agent There is a possibility that the bubbles of the lead may cause false detection of cracks. Therefore, it is preferable to remove the polishing agent adhering to the surface of the wafer W before removing the wafer W from the carrier 4 (step (C) in FIG. 2).

The polishing agent adhering to the surface of the wafer W is effectively removed by at least one of the method of applying water to the wafer W, rotating the lower surface plate 8b, and rotating the carrier 4. Can do. For example, as shown in FIG. 4, by blowing water from the nozzle 20 onto the wafer W, it is possible to effectively remove the abrasive bubbles on the surface. In addition, as means for applying water to the polished wafer W, a spray nozzle conventionally used to keep the polishing cloths 9a and 9b moisturized may be used, or slurry supplied to the upper surface plate 9a may be supplied. The holes 33 may be used.
In addition, the abrasive or water adhering to the surface of the wafer W may be removed by rotating the lower surface plate 8b or by rotating the carrier 4 without applying water or after applying water. good.

After removing the abrasive, the wafer W is held by the transfer robot 13 and taken out from the carrier 4 (step (D) in FIG. 2).
As described above, if the transfer robot 13 is provided with a holding unit that sucks the surface of the wafer W, the polished wafer W can be reliably sucked and held from the carrier 4.

Next, before being transported to the unloading station 16, the crack inspection means 12 inspects whether or not the wafer W is cracked while being held by the transport robot 13 (step (E) in FIG. 2).
When performing the inspection, as shown in FIG. 3, the illumination unit 22 applies light to the surface of the wafer W while being held by the transfer robot 13. At this time, if the wafer W is held horizontally, water or the like may remain attached to the wafer surface, leading to erroneous detection. Therefore, it is preferable to hold the wafer W vertically (or inclined) for draining water.

  The surface of the wafer W irradiated with light is photographed by the CCD camera 21, and the obtained image data is sent to a computer 23 for image processing. Then, the image processed by the computer 23 is displayed on the monitor. At this time, if the wafer W is cracked, there is a difference (light / dark) in the brightness / darkness of the image between the unbroken portion and the cracked portion. Can be determined. For example, the determination circuit 24 may determine that “there is a crack” when there is an area brighter than other areas in the wafer surface (step (F) in FIG. 2).

  The inspection area may be the entire wafer surface, but the outer edge is chamfered or has an orientation flat or notch for positioning, etc. There is a risk that. Therefore, as shown in FIG. 5, for example, as shown in FIG. 5, cracks are caused by light and darkness in a region between the circular (or elliptical) double lines 27 a and 27 b set inside the outer edge of the wafer W. Presence / absence can also be determined.

When cracks occur in the wafer W, cracks often enter from the periphery, so that cracks are included in the region between the double lines 27a and 27b set as described above. If only the area between 27b is set as the inspection target area, the inspection area is narrow, and therefore the presence / absence of cracks can be reliably determined in a shorter time. The double lines 27a and 27b are preferably set as large as possible so that small cracks and chips generated in the peripheral portion of the wafer W can be detected, but the closer to the outer edge of the wafer W, the smaller There is a possibility that the outer edge portion may be determined as a crack when it shifts to. Therefore, for example, when the notch 28 is formed in the wafer W, it is preferable to set the regions of the double lines 27 a and 27 b inside the notch 28.
The width between the double lines 27a and 27b may be set as appropriate. For example, when one pixel is 1 mm wide, the width can be set to 5 mm to 10 mm (5 to 10 pixels).

As described above, after the polished wafer W is held by the transfer robot 13, the wafer W is inspected for cracks, and then the wafer W is recovered. However, no crack is detected in the wafer W in which the crack is detected. It is preferable to provide a means for collecting separately from the wafer W.
For example, as shown in FIG. 1, a broken wafer collection container 19 is provided separately from the regular collection container 17 in the unloading station 16, and if it is determined by the determination circuit 24 that there is a crack, the transfer robot 13 is set so that the wafer is automatically accommodated in the broken wafer collection container 19.
Alternatively, when a crack of the wafer is detected, the operation of the transfer robot 13 is set to stop, and the worker confirms the crack of the wafer and puts it in the collection container 19 or collects it by hand. You may do it.

  Furthermore, as shown in FIG. 3, an alarm means 25 that emits an alarm sound when a crack is detected may be provided. If such an alarm means 25 is provided, it is not necessary for the worker to constantly monitor, the occurrence of cracks can be immediately recognized, appropriate measures such as stopping the operation of the device and investigating the cause. Can be taken.

The wafer in which no crack has been detected is accommodated in the collection container (water tank) 17 of the unloading station 16 by the transfer robot 13 (step (G) in FIG. 2).
Then, all the wafers in the carrier 4 are inspected for cracks as described above (step (H) in FIG. 2).

  When the inspection of all the wafers of the carrier 4 is completed, the wafer W of the next batch is taken out from the box 11 of the loader unit 10 and set on the carrier 4 in the same manner as described above. And after grinding | polishing, the presence or absence of a crack is test | inspected.

  When all the wafers W in the same box are polished and accommodated in the collection container 17, they are transferred to the next process (cleaning) by the automatic transfer device (AGV) 18.

  As described above, according to the double-side polishing apparatus 1 according to the present invention, the inspection table includes the means 12 for inspecting whether or not the wafer is cracked while the polished wafer is held by the transfer robot 13. The wafer can be reliably inspected in a short time without being placed on the surface. Moreover, it is not contaminated by being placed on a table or the like after polishing. Therefore, after polishing the wafer, it can be collected in a short time, the polishing operation can be performed very efficiently, and the wafer quality can be improved.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

For example, the arrangement in the polishing apparatus is not limited to that shown in FIG. In addition, the transfer robot may be provided separately for loading and unloading.
Further, the present invention is not limited to the swing type double-side polishing apparatus, and can also be applied to a four-way type double-side polishing apparatus and other types.
Further, as a means for inspecting cracks in the wafer, it is possible to use an LED as a light source and to detect cracks with a light receiving sensor such as a photodiode.

It is the schematic which shows an example of the double-side polish apparatus which concerns on this invention. It is a flowchart which shows an example of the double-sided grinding | polishing process which concerns on this invention. It is a schematic block diagram which shows an example of the crack test | inspection means based on this invention. It is the schematic which shows an example of a water injection nozzle. It is the schematic which shows an example of the double line set as a crack inspection area | region. It is a schematic diagram showing an example of a 4-way double-side polishing apparatus. It is a schematic plan view which shows a planetary gear structure. It is the schematic of a rocking | swiveling type double-side polish apparatus. It is a schematic plan view of the carrier holder in the swing type double-side polishing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Double-side polish apparatus, 2 ... Polishing apparatus main body, 3 ... Carrier holder, 4 ... Carrier,
5 ... Holding hole, 6 ... Slurry passage hole, 7 ... Eccentric arm, 8a, 8b ... Surface plate,
9a, 9b ... polishing cloth, 10 ... loading station (loader part),
11 ... Wafer storage box, 12 ... Crack inspection means, 13 ... Transfer robot,
14 ... Box automatic transfer device, 15 ... Centering stage,
16 ... unloading station (unloader part),
17 ... Recovery container (water tank), 18 ... Automatic transfer device,
19 ... Container for collecting broken wafers, 20 ... Water injection nozzle,
21 ... Image detection means (CCD camera), 22 ... Illumination means,
23 ... Image processing means (computer, monitor) 24 ... Determination means (determination circuit),
25 ... Alarm means, 27a, 27b ... Double wire, 33 ... Slurry supply hole,
W ... wah.

Claims (7)

A double-side polishing apparatus for a semiconductor wafer, comprising at least upper and lower surface plates, a polishing cloth affixed to each surface plate, a carrier for holding the wafer between the upper and lower polishing cloths during polishing, and before and after polishing A transfer robot for transferring the wafer, a nozzle for spraying water for removing the abrasive on the surface of the polished wafer, and the polished wafer in a state where the wafer is held vertically or inclined by the transfer robot. Inspect for the presence or absence of cracks in the entire area of the opposite surface of the holding surface of the wafer, or between the circular or elliptical double lines set inside the outer edge of the opposite surface of the holding surface of the wafer A double-side polishing apparatus characterized by comprising:   The means for inspecting the presence or absence of cracks in the wafer includes illumination means for irradiating light on the surface of the polished wafer, image detection means for detecting an image of the wafer, and image data obtained by the image detection means. 2. The double-side polishing apparatus according to claim 1, further comprising: image processing means for image processing; and determination means for determining whether or not the wafer is cracked based on brightness of the image processed image.   The double-side polishing apparatus according to claim 1 or 2, wherein the image detection means is a CCD camera or a vidicon camera.   When the means for inspecting the presence or absence of cracks in the wafer detects cracks, there are means for collecting the wafers separately from the wafers for which no cracks have been detected and / or means for stopping the operation of the transfer robot. The double-side polishing apparatus according to any one of claims 1 to 3, wherein the double-side polishing apparatus is provided.   5. The double-sided device according to claim 1, further comprising alarm means for generating an alarm sound when the means for inspecting the wafer for cracks detects a crack. 6. Polishing equipment. After polishing a semiconductor wafer with a double-side polishing machine, this method is used to inspect the polished wafer for cracks. The semiconductor wafer is set on a carrier and held between polishing cloths attached to upper and lower surface plates. Then, the polishing agent is supplied and the upper and lower polishing cloths are slidably contacted to perform polishing, water is applied to the polished wafer, the lower surface plate is rotated, and the carrier is rotated. The method removes the polishing agent from the surface of the wafer, holds the wafer by a transfer robot , removes the wafer from the carrier , and then vertically or tilts the wafer by the transfer robot before transferring to the unloading station. and while holding the entire surface of the opposite surface of the holding surface of the wafer, or on the opposite side surface of the holding surface of the wafer Method of inspecting cracks in the semiconductor wafer, characterized in that for checking the presence or absence of cracks in the region between the outer edge than set inside a circular or oval doublet. Inspecting the presence or absence of cracks in the semiconductor wafer, illuminating the surface of the wafer, subjecting the image data obtained by the image detection means to image processing, and inspecting the presence or absence of cracks in the wafer based on the brightness of the image A method for inspecting cracks in a semiconductor wafer according to claim 6 .

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